Art of cracking hydrocarbon oils



July 17, 1928. 1,677,775

E. c. HERTHEL ET AL.

ART orf cRAcKING HYDRocARBo mns` Filed Aug. l2, 1927 ww .mw

me WN ATTORNEYS Patented July 17, 1928.

UNITED STATES PATENT OFFICE.

EUGENE C. HERTHEL AND THOMAS 1,DE COLON TIFIET, OF CHICAGO, ILLINOIS, AS-

SIGNORSy TO SINCLAIR REFINING COMPANY, F NEW YORK, N. Y., A CORPORATION OF MAIN E.

ART OF CRACKING HYDROCARBON OILS.

Application filed August 12, 1927. Serial No. 212,482.

This invention relates to improvements in the cracking of heavier and higher boiling hydrocarbon oils, such as gas oil, to produce therefrom lighter and lower boiling hydrocarbon oils, such as gasoline and gasoline-containing pressure distillates. The invention includes an im roved method of cracking hydrocarbon 011s, improvedi features of operation, and an improved apparatus.

In carrying out the present invention, a body of oil is maintained in a vaporizing zone under a superatmospheric pressure and'at'a cracking temperature and vapors including vapors ofl the cracked product are taken ofi` from this vaporizing zone Vunder pressure Oil is forced into this vaporizing zone through heating tubes in which it is heated to a cracking temperature. The

oil forced through these heating tubes may be a mixture of raw oil and reflux condensate refluxed from the vapors taken off from the vaporizing zone, and it may also include oil re'circulated through these heating tubes from the vaporizing zone. Residual oil is discharged from this first vaporizing zone into a separate vaporizing zone maintained under a pressure lower than that prevailing in the first, and the vapors separated under this lower pressure are taken off and subjectedto a condensing operation. This condensing operation may be a fractionating operation through which lighter components of the vapors are permitted to pass uncondensed. Condensate from the condensing operation to which the vapors from the second vaporizing zone are subjected is then forced through separate heating tubes into the first vaporizing zone. The heating gases for supplying heat to the cracking operation are passed first over these separate heating tubes through which condensate from the condensing operation to which the vapors from the second vaporizing zone are l5 subjected is passed and then over the first mentioned heating tubes. The heating tubes through which the condensate from the vapors separated from the residual oil in the second vaporizing zone is circulated are i0 thus exposed to the heating gases while at highest temperature and the heating gases contact with the remaining heating tubes through which raw oil and reflux condensate from the first vaporizing zone and any oil recirculated from the first vaporizing zone are passed only after reduction in temperature due to heat absorption by the heating tubes with which the heating gases first contact.

The second vaporizing zone is advantageously externally unheated and the vaporization therein effected by the self-contained heat of the residual oil on reduction of pressure. The vaporization in the second vaporizing zone may be'carried so far that the unvaporized residue remaining is of cokelike character or it may be restricted so that the unvaporized residue can be discharged from the second vaporizing zone as a fiuid pitch or tar. The vaporization in the second vaporizing zone can be controlled by regulating the pressure therein. Where the vaporization is carried to a point such that the unvaporized residue remaining is of a coke-like character. a plurality of separating vessels Aare provided to avoid interference with continuit of operation. The first vaporizing zone a so is advantageously externally unheated.

In addition to the desired lighter and lower boiling hydrocarbon oils, the products of the cracking operation include heavy asphaltic and pitch-like constituents which tend to form deposits on the heating surfaces of cracking stills with consequent dangerof overheating the surfaces on which such deposits occur. This effect is cumulative. Usually, the formation of such carbonaceous deposits is the limiting factorl in determining the useful `period of operation as they necessitate periodic shut down for cleaning. These asphaltic and pitch-like constituents are formed progressively as the cracking o eration continues, and unless they exceed tfie saturation point they may be largely maintained in solution in the charge of oilnin the cracking still. The useful period of bperation of the cracking still can be materially prolonged, as described in Letters Patent No. 1,598,136 issued to the Sinclair Refining Company, August 31, 1926, by appropriately regulating the supply of fresh oil to and the discharge of pitch-laden oil from the charge of oil in the cracking still. This vmethod of operation, however, requires the discharge from the pressure still of a large amount of residual pitch-laden oil and this residual oil also includes a substantial proportion, frequently a predominating'proportion, of oil constitutents suitable for further cracking to produce further quantities of the desired lighter and lower boiling hydrocarbon oils.

In carrying out the present invention, the coneentrationof asphaltic and pitch-like constituents in the body of oil in the first vaporizingzone may be kept below an objectionable value or below saturation as described in said Letters Patent No. 1,598,136, 4and the oil constituents suitable for further cracking ofthe residual oil discharged from the first vaporizing zone returned to the cracking operation in a. particularly advantageous Inanner. The asphaltic or pitch-like constituents of the residual oil are separated in the second vaporizing Zone, and the oil vconstituents vaporized to a greater orless extent from this residual oil in the second vapor- 'izing zone are condensed and returned to the first vaporizing zone after again being heated to a cracking temperature. The return of oil constituents discharged from the first vaporizing zone with the residual oil may thus be effected with very little heat loss. Likewise, in carrying out the invention, these returned oil constituents which are somewhat refractory to further cracking are subjected to relatively severe and advantageous cracking conditions and are also employed to assist in protecting the heating tubes through which' raw oil and refiux condensatev and any recirculated unvaporized oil are' discharged into the first vaporizing zone.

In carrying out the invention, the vapors from the first vaporizing Zone are subjected to a refiuxing operation lfrom which reflux condensate is returned to the first vaporizing zone through the first mentioned heating tubes. Raw oil may be supplied to the stream of refiux condensate fiowing back to these heating tubes, or the raw oil supplied to the operation, or part'of it, may be introduced into the vapors inthe refluxing operation for preheating the raw oil and refiuxing the vapors. This refluxing operation, for example, 4'is advantageously controlled by the regulated introduction of raw oil in this manner. Additional raw oil may then be supplied to the stream of reflux condensate and admixed raw oil flowing through these heating tubes. This refluxing operation, however, may be effected and controlled by other cooling means. The condensing operation to which the vapors from the second vaporizing zone are subjected :may be a refluxing or' fractionating operation, and this operation Ialso may be controlled by regulated introduction of a part of the raw oil supplied to the operation. This refiuxing or fractionating operation, however, may with advantage beeflected or controlled by return and reintroduction into the vapors in this refiuxing or fractionating operation of a part of the distillate product, either from the refiuxing operation to which the vapors from the first vaporizing Zone are subjected or from the refiuxing operation to which the vapors from the secondvaporizing zone are subjected or from both. This second refluxing or fractionating operation also .may be effected or controlled by other cooling means.

The invention is of special value and application in connection with pressure cracking stills of the general type described in Letters Patent No. 1,285,200 issued to the Sinclair Refining Company, November 19, 1918, and it will be further described more particularly in connection therewith. The pressure still system illustrated in the accompanying drawings is of the general type described in said Letters Patent No. 1.285,- 200, and includes in addition an auxiliary bank of heating tubes arranged in the path of the heating gases between the firebox and the heating tubes of the pressure still proper, as described in application Serial No. 664,502 filed September 24, 1923. In certain aspects, however, the invention has advantages which are of more general application.

The invention will be further described in connection with the accompanying drawings which illustrate, in a diagrammatic and conventional manner, in elevation and partly in section and with parts broken away, a pressure still system embodying the invention and adapted for the practice of thel invention.

Referring to the drawings, the pressure still system illustrated comprises a bulk supply drum 1, a battery of heating tubes 2 arranged in the heating fluesof a furnace 3 and circulating connections 4, 5v and 6including a circulating pump 7 arranged to provide for circulation of oil from the bulk supply drum 1 upwardly through the heating tubes 2 and back to the bulb supply drum. An auxiliary bank pf heating tubes 8 is arranged in the furnace in the path of the 4heating gases between the fireboX 8 and' i the heating tubes 2. Beforepassing lover the heating tuhes2, heating gases including fresh hot products of combustion from the firebox 9 are thus tempered by heat absorbed in the separate bank of heating tubes 8. Further to assist in tempering the heating gases, a portion of the waste heating gases about to escape through the stack flue 10 may be returned and admixed with the fresh hot products of combustion from the firebox through the return fiue 11, provided with suitable forcing means such as a steam jet or fan. The auxiliary bank of heating tubes 8 is arranged to discharge into the. bulk .supply drum 1 throughconnection 12 and the return circulating connection 6.

Vapors from the bulk supply drum 1 escape through connection 13 and pass upwardly through the reflux tower 14, uncondensed vapors escaping from the upper end lon turned from the reflux tower 14 through connection 21 to the circulating connection 4 connecting the bulk supply drum with thesuction side of the circulating pump 7.

Unvaporized residual oil is discharged from the bulk supply drum 1 through connection 22 into the separator 23. A pressure reducing valve 24 is provided in connection 22, advantageously at a point adjacent the bulk supply drum, to control and reduce the pressure between the bulk supply drum 1 and the separator 23. To promote vaporization, steam, or other heated gaseous medium, may be introduced into the separator 23. lFor example, steam may be injected into and admixed with the residual oil troni 'the bulk supply drum as it enters the sep` ara-tor. As little as 1% of steam will, in many cases, materially increase the amount of vaporization over any particular pressure drop. To inhibit entrainment, several baffles or other suitable means may be arranged in the upper end of the separator 23.

Connection 25 is provided for .the dis-l charge, for example through suitable cooling means, of fluid residues from the separator 23'. Vapors escape from the separator 23 through connection 26 to a point somewhat above' the lower end of the reflux tower 27. Vapors escaping uncondensed from the upper end of reflux tower 27 pass through cnnection 28 to condenser 29 arranged to discharge into receiver 30. Connection 31 is provided for the discharge of condensate and connection 32 for the discharge of uncondensed vapors and gases from this receiver. To ell'ect or control condensation in the tower 27, a part of the condensate from either or bothof the receivers 17 and 30, or a light oil of similar character, may be introducedl into the upper end of this towervthrough connection 33.

Condensate collecting in the lower end of the reflux tower 27 is forced by means vof pum 34 through the auxiliary bank of heating tubes 8 and thence into the bulk supply drum 1. Condensate from the tower 27 passes to the Dump through connection 35 and is discharged from the pump into the heating tubes 8 through connection 36, Additional oil may be supplied to the heating tubes 8 through connection 37, and a part of the reflux condensate from tower 27 may be discharged through connection 38, as required. It is advantageous to lprovide suitable storage space for hot reflux condensate from the tower 27 for example in the lower end ofl tower 27, to promote uniformity of operation.

The pressure in the bulk supply drum 1 may. be maintained and regulated by valve 39 inv the vapor connection between the reflux tower 14 and the condenser 16, or by suitable valves arranged beyond the condenser or receiver. Cool oil for cooling and lubricating the bearings of the -circulating pump 7 may be supplied through connection 40, or an amount of raw oil in excess of that required for cooling and lubricating the circulating pump bearings may be introduced into the circulating oil throu h this connection. Connection 41 is provi ed for pumping out the still at the end of a run and for initially charging the still at the beginning of a run. Connection 42 is provided for draining .the auxiliary bank of heating tubes 8. Suitable valves, 43 and 44, for cx# ample, are provided whereby the pressure in the separator 23 may be regulated and controlled. The hot parts of the apparatus,

including the bulk supply drum 1 and the vapor separating chamber 23 as well as the various hot connections, are advantageously lagged or heat insulated to prevent heat loss. In particular, the vapor separating chamber 23 is advantageously heavily lagged or heat insulated. To promote condensation, the reflux tower 27 may be left uninsulated, although control is somewhat facilitated if this tower is also insulatedagainst heat loss.

In carrying out the invention in the apparatus illustrated, a body of oil is maintamed under a superatmospheric pressure and at a cracking temperature in the bulk supply drum 1 of high pressure vaporizing zone and vapors are taken off from this vaporizing zone under pressure, oil from this body is circulated through the heating tubes 2 in which it is heated to a cracking temperature and back to the body, residual oil is discharged /from this body into the separator 23 or second vaporizing zone in which vapors are taken off under reduced pressure, these vapors are subjected to a condensing operation in the reflux tower 27 and the condensate from this condensing operation is 'forced through the separate heating tubes 8 into the bulk supply drum 1 or first vaporizing zone, and the heating gases from the fire box 9, in which fuel is burned for supplying heat to the cracking operation, are passed first over the heating tu es 8 and then over the heating tubes 2. Reflux condensate from reflux tower 14, together with any admixed unvaporized raw oil introduced through connection 20, is returned to the body of oil circulating through the heating tubes 2 through connect-ion 21.

In operation, the pressure still is charged with raw oil and the charge is gradually y before the concentration of brought to cracking conditions of temperature and pressure in the usual way. In a still of the type illustrated, an initial charge -ot' about 8,000 gallons of cold oil, that is oil lat a temperature of about 80 F. for example, is commonly used. During the initial period of operatlon, or until an adequate supply of condensate from tower 27 is available, oil may be circulated through the heating tubes 8 from thedischarge side of the circulating pump 7 by means of the by-pass connection 45, or raw oil may be pumped into the still through these heating tubes by means of pump 34 dauring this period of operation. The pressure maintained on the bulk suppl drum 1 during operation is determine to a large measure by the stocks to be treated and the products to be obtained. With gas oil character charging stocks, and for the production of gasoline, pressures up to 125,. ounds per square inch or more may be use and with chargingstocks containing large amounts of kerosene character components much higher pressures, say-up to 300 pounds er square inch or more, may be used. hen the still is brought to operating conditions, the introduction of raw oil through connection 20 is begun, and the supply of raw oil through thislconnection is regulated to condense in the reflux tower 14 those components of the vapors heavier 0r higher boiling than desirable as components of the distillate product. The discharge of unva orized oil'from the still may be omitteddurlng the initial period of operation or may be in but small amount, but

pitch-like constitutents in the charge of oil 1n the ressure still reaches an objectionable value, t e withdrawal of pitch-laden oil in substantial amount is begun and the rate of Withdrawal of pitch-laden oil and the supply of' raw oil is regulated to maintain the concentration of pitch in the pressure still char e below an objectionable value. The pitc laden oil is discharged into the separator 23 where a pressure substantially lower than that prevailing within the bulk supply drum 1 is maintained, the pressure being reduced by means of valve 24. Due to this reduction.

in pressure, the withdrawn pitch-laden oil is subjected to vaporization, the vapors en- A tering the tower 27 and pitch components separating as a residue remaining unvaporized. The degree ofl vaporization can be controlled by regulatin the pressure. As much as 80% or more oY the pltch-laden oil may be so vaporized by its self-contained heat, but if a liquid residue is to be maintained it is usually not desirable to go much beyond this point and it may be necessary to reduce the amount of vaporization, although a 1i uid residue can sometimes be obtained. wit vaporization of as much as low atmospheric sures in the neighborhood of 100 pounds per square inch or higher, the rcssure in the separator 23 may be maintained at a value between atmospheric pressure and say 50 pounds per square inch or higher, depending upon .the amount of vaporization desired, or the pressure in the separator 23 may be maintained at a value somewhat beressure. When the discharge of pitch-la en oil into the separator 23 is begun, and the vapors separated from this residual oil begin to pass through the tower 27, condensation in tower 27 is begun and the condensate is forced through the heating tubes 8. It the amount of such condensate -is -for any reason insufficient, additional raw oil may be supplied to the heating tubes 8 in admlxture therewith through connection 37 Such raw oil may also be introduced into the reflux tower through connection 33 to assist in promoting condensation therein. The introduction of a lpart of the distillate product, or such raw oil, or other refiuxing medium into the re.- Hux tower 27 through connection 33 is regulated to effect condensation of those heavier and higher boiling components of the vapors suitable for further cracking. for the production of gasoline, or gasolinecontaining pressure distillates, with a gas oil character charging stock, with a still pressure in the neighborhood of 125 pounds per square inch, the temperature at the top of reflux tower 14 may be maintained in the neighborhood of 500 to 550o F. and the temperature at the top of the reflux tower 27 in the neighborhood of 350 to 400o F. Distillate may be vtaken off'through connection 18 at a rate, for example, in the neighborhood of 1,000 gallons per hour, pitch- Operating laden residual oil discharged from the bulk supply drum 1 to the se arator 23 at a rat-e in the neighborhood o 1,500 gallons per hour, and raw oil supplied at a rate sucient to maintain the still charge; Raw oil in excess of that required to maintain the desired temperature at ythe top of the reflux towers may be introduced 'for example, through connection 40, or through connection 37.

The invention has several important advantages. It provides important heat economies particularly in connection with operations of the type described in said Letters Patent No. 1,598,136. It provides for in- -creased continuity of operation without saclll).

iso

and unvaporized oil is not recirculated through these auxiliary heating tubes. At the same time, the invention provides for advantageous treatment of the several types of stocks circulating in the pressure still system. The relatively refractory condensate from the vapors separated under reduced pressure from the residual oil dis` charged from the pressure still proper is subjected to the most severe cra-cking conditions. Raw oils of more refractory character may also be supplied first to these auxiliary heating tubes while raw oil of less refractory character is supplied direct-ly to t-he'pressure still proper.

We claim:

1. An -improved method of cracking hydrocarbon oils, which comprises maintaining a body of oil in a vaporizing zone under a superatmospheric pressure and heating it to a cracking temperature by circulatin oil therefrom through heating tubes and ack thereto, taking off vapors including vapors of the cracked product therefrom under pressure, discharging oil from the said body into a separate vaporizing zone maintained under a pressure lower than that prevailing in the first and taking off vapors from the second vaporizing zone, subjecting the vapors from the second vaporizing zone to a. condensing operation and forcing condensate from this condensing operation through separate heating tubes into the first vaporizing zone, and passing heating gases from a irebox in which fuel is burnedrfor supplying heat to the cracking operation first over the heating tubes through which condensate from the said condenslng operation is forced and then over the heating tubes throu h which oil from the said body is cireulate 2. An improved method of cracking hydrocarbon oils, which comprises maintaining a body of oil in a vaporizing zone under a superatmospheric pressure and at a cracking ,temperature and taking off vapors including vapors of the cracked product therefrom under pressure, forcing oil into the said vaporizing zone through heating tubes and heating it to a cracking temperature therein, discharging oil from the said body into a separate vaporizing zone maintained under a pressure lower than that prevailing in the first and taking off vapors .from the secondiI vaporizin zone, subjecting the vapors from the secon vaporizing zone to a condensing operation and forcing condensate from .this condensing operation through separate heating tubes into the first vaporizing zone, and passing heating gases from a fireboX in which fuel is burned. for supplying heat to the cracking operation first over the heating tubes through which condensate from the said condensing operation is forced and then over the first mentioned heating tubes.

3. An improved method of cracking hydrocarbon oils, which comprises maintaining a bodyT of oil in a vaporizing zone under a superatmospheric pressure and at a cracking temperature, taking ofi vapors including vapors of the jcracked product therefrom under pressure and subjecting these vapors' to a refluXing operation, forcing oil including reiux condensate from the said refluxing operation into the said vaporizing Zone through heating tubes and heating it to a cracking temperature therein, discharging oil from the said body into a separate Vvaporizing zone maintained under a pressure lower than that prevailing in the first and taking off vapors from the second vaporizing zone, subjecting the vapors from the second vaporizin zone to a condensing operation and forcin condensate from this condensing operatlon through separate heating tubes into the first vaporizing zone, and passing heating gases from a firebox in which fuel is burned for supplyinor heat to the cracking operation first over thetheating tubes through which condensate from the said condensing operation is forced and then over the first mentioned heatin tubes.

4. An improve method of cracking hydrocarbons oils, which comprises maintaining a body of oil in a vaporizng Zone under a superatmospheric pressure and at a cracking temperature, taking off vapors including vapors of the cracked product therefrom under pressure and subjecting these vapors to a reiiuxing operation, introducing raw oil into the vapors in this refluxing operation, forcing oil including admixed reflux condensate and unvaporized raw oil from this refluxing operation into the said vaporizing zone through heating tubes and heating it to a cracking temperature therein,\dis charging oil from the said body into a separate vaporizing zone maintained under a pressure lower than that prevailing in the first and taking off vapors from the second vaporizing zone, subjecting the vapors from the second vaporizing zone to a condensing operation and forcing condensate from this condensing operation through separate heating tubes into the first vaporizing zone, and passing heating gases from a rebox in which fuel is burned for supplying heat to the cracking operation first over the heating tubes through which condensate from the said condensing operation isiforced and then over the first mentioned heating tubes.

5. An improved method of cracking hydrocarbon oils, which comprises maintaining a body of oil in a varporizing zone under a superatmospheric pressure and at a cracking temperature and taking ofi' vapors including vapors of the cracked product therefrom under pressure, forcing oil into the said vaporizing Zone through heating tubes and heatingr it to a cracking temperature therein, discharging oil from the 'said body into a separate externally unheated vaporizing zone maintained under a pressure lower than that prevailing in the first and 4taking off vapors from the Isecond vaporizing zone, subjecting the vapors from the second vaporizin'g zone to a condensing operation and forcing condensate from this condensin operation through separate heating tu es into the first vaporizing zone, and passing heating gases from a fire-box in which fuel is burned for supplying heat to the cracking operation first over the heating tubes through which condensate from the said condensing operation is forced and then over the first mentioned heating tubes.

6. An improved method of cracking hydrocarbon oils, lwhich comprises maintaining an externally unheated body of oil in a vaporizing zone under a superatmospheric pressure and at a cracking temperatu're and taking off vapors including vapors of the cracked product therefrom under pressure, forcing oil into the said Vaporizing zone through heating tubes and heating it to a cracking temperature therein, discharging oil from the said body into separate externally unheated vaporizing zone maintained under a pressure lower than that prevailing in the first and taking off vapors from the second vaporizing zone, subjecting the vapors from the second vaporizing zone to a condensing operation and forcing condensate from this condensing operation through separate heating tubes into the first vaporizing zone, and passing heating gases from a firebox in which fuel is burned for supplying heat to the cracking operation first over the heating tubes through which condensate from the said condensing operation is forced and then over the first mentioned heating tubes.

Y 7. An improved method of cracking hydrocarbon oils, which comprises maintaining a body of oil in a vaporizing zone under a superatmospheric pressure and heating it to a cracking temperature by circulating oil therefrom through heating tubes and back thereto, taking off vapors including vapors of the cracked product therefrom under pressure and subjecting these vapors to a refiuxing operation, returnin refiux condensate therefrom to the sai body of oil and separately condensing vapors remaining uncondensed therein, discharging oil from the said body into a separate vaporizing zone maintained under a pressure lower than that prevailing in the first and taking off vapors from the second vapori'zing zone, subjecting the vapors from the second vaporizing zone to a separate re- .fiuxing operation and forcing refiux condensate therefrom through separate heating tubes into the first vaporizing zone, separately condensing vapors remaining uncondensed therein, and passing heating gases from a ing heat to the cracking operation first over the heating tubes through which condensate from the said condensing operation is forced and then over the heating tubes through which oil from the said body is circulated.

8. An improved apparatus for cracking oil, comprising a heating furnace having a heating flue and a fireboX connected to one end of the heatin flue, a bulk supply drum and a battery of eating tubes arranged in the said heating flue and circulating connections v for circulating oil from the bulk supply drum through the heating tubes ana back to the bulk supply drum, means for taking off vapors from the bulk supply drum under pressure, a separator and connections including pressure reducing means between a point in the bulk supply drum below the normal liquid level therein and the separator, a vapor outlet from the said separator, condensing means and connections between the vapor outlet from the separator and the said condensing means, a separate bank of a heating tubes arranged in the said heating fine between the fireboX and the first mentioned heating tubes, connections between one end of this bank of heating tubes and the bulk supply drum, and connections including a forcing means for supplying condensate from the said condensing means to the other end of the said separate bank of heating tubes.

9. An improved apparatus for cracking oil, comprising a heating furnace having a heating' flue and a firebox connected to one end of the heating Hue, a vapor separating chamber, means for takin off vapors therefrom under pressure, heatmg tubes arranged in the said heating flue and discharge connections therefrom to the said vapor separating chamber, connections including a forcing means for circulating oil through the said heating tubes into the said vapor separating chamber, a second vapor separating chamber, connections including pressure reducing means between a point in the first said vapor separating chamber below the normal liquid level therein and the second said vapor separating chamber, condensing means and a vapor connection between the second said vapor separating chamber and this condensing means, separate heatingl heating Hue and a rebox connected to one end of the heating flue, an externally yunheated va or separating chamber, means for taking o heating tubes arranged in the said heating vapors-therefrom under pressure,

ilue and discharge connections therefrom to `fthe'said vapor separating chamber, connections including a forcing means for circulatlevel therein and the second said vapor lseparating chamber, condensing means and a vapor connection between the second said vapor separating chamber and this condensing means, separate heating tubes arranged in the said heating fluev between the firebox and the rst mentioned heating tubes and discharge connections therefrom to the first said vapor separating chamber, and connections including a forcing means for circulating condensate from the said condensing means through the said separate heating tubes into the first said Vapor separating chamber.

i EUGENE C. HERTHEL.

THOMAS DE COLON TIFFT. 

